Cheat Engine

rkubes · How do I cheat? Reputation: 0 Joined: 08 Dec 2014 Posts: 8

Hello,

There is an instruction that exists in the game I was hacking as follows:
F3 41 0F5C C4 - subss xmm0,xmm4

Say I change that to nop, then I tell Cheat Engine to change it back, when I type "subss xmm0, xmm4" I get a different byte code

F3 0F5C C4 - subss xmm0,xmm4

Notice the 41 missing.

This produces much different results.

Really even if I double click the original instruction and just hit enter, Cheat Engine wants to change it from 5 bytes to 4 bytes.

Does anyone have any insight on what the difference is?

In this particular case, xmm0 = 30.00, and xmm4 = 108.61 as a float; when the correct instruction runs, xmm0 is 29.95 (not sure where the 0.05 came in). When the incorrect (CE) instruction runs, xmm0 is set to -78.61 (as you would expect). However, this produces undesired behavior in-game.

Any assistance or insight will be greatly appreciated! I know in the mean time I can just tell CE which bytes to write, but I would like to know what's going on. Thanks!

++METHOS · Posted: Sat Dec 13, 2014 5:06 am Post subject:

Don't manually edit the bytes...let CE fill the code with NOP's for you...then, when you change it back, let CE build the code back for you. You shouldn't have to type anything.

rkubes · How do I cheat? Reputation: 0 Joined: 08 Dec 2014 Posts: 8

Thanks for the suggestion, the problem is Cheat Engine seems to be reporting the original code wrong from the bytes.

After further investigating I was able to determine the following:

The original Byte Code is
F3 41 0F5C C4

This actually translates to: subss xmm0,xmm12

However, the CE disassembler thinks it means: subss xmm0,xmm4

If I manually type in "subss xmm0,xmm12" Cheat Engine assembles it correctly (but even after the change still reads the instruction as "subss xmm0,xmm4")

Just a display bug

Dark Byte · Posted: Sat Dec 13, 2014 7:10 am Post subject:

This seems to be already fixed in the svn